Add HTTP API server, Android app, and CI build/publish pipeline

- docker-compose.yml + tooling-container/src/server.py: serve
  preprocess/OCR/extract over an async job API (POST /jobs, GET
  /jobs/{id}) instead of manual host-script runs per receipt
- android/: Kotlin/Compose app - capture a receipt photo, poll job
  progress, review/edit extracted fields, save locally (Room), export
  to CSV/ODS
- .gitea/workflows/build.yml: build the debug APK and publish it to
  dl.ladkau.de on push
- build-image.sh: also pull ollama/ollama so all pipeline images are
  ready after one script
- add project logo (also used for the app's launcher icon/splash)

.gitignore

@@ -17,3 +17,18 @@
 # instead of run through the container)
 __pycache__/
 *.pyc
+
+# Android app build output/local config and generated resources (launcher
+# icon + splash art - see android/app/build.gradle.kts's
+# generateAppIcons task and android/scripts/gen_app_icons.py's own
+# doc comment).
+/android/local.properties
+/android/.gradle
+/android/build
+/android/app/build
+/android/app/src/main/res/drawable-nodpi
+/android/app/src/main/res/mipmap-mdpi
+/android/app/src/main/res/mipmap-hdpi
+/android/app/src/main/res/mipmap-xhdpi
+/android/app/src/main/res/mipmap-xxhdpi
+/android/app/src/main/res/mipmap-xxxhdpi